cat heading team resources

team resources classifying audio iconEVP are probably the most prolific results produced by paranormal investigations.  There are good things about this, and there are bad things.  The bad news is that, working under the assumption evidence of the paranormal is a rarity, with so many examples of EVP populating the internet, the likelihood any of it being genuinely "paranormal" is pretty low.



The good news? With as much EVP as we claim to capture, we have the luxury of parsing it of only the best and the strongest examples, which leads to a data set that, once again, is strong enough to be considered potentially compelling.  It's analogous to how photographers rely on contact sheets by the dozens to pick out just the strongest image to represent them.

And this is where EVP classification goes to the heart of the matter, by grading the risk factor to credibility.

People often look to classifying EVP to establish their sound quality, as though they were grades of maple syrup. However, the truth is, EVP classification ultimately grades a degree of risk anyone is taking in expressing interest the data as potentially paranormal.  To put it in plainer terms:  we are more certain about a Class A EVP being a potential indicator of something paranormal than we are about a Class B EVP, and a Class C EVP is even less certain yet. (Readers should note, indicating an audio event's potential to be paranormal isn't the same as saying it's actually paranormal, regardless of how impressive it may seem.)


Events of Interest

Before we go any further, I’d like to say a word about a word: evidence. (I know, I know—you’re thinking, Please not another pretentious discussion about language! but because I’m an actual English professor and a writer, I ain’t pretending, so I get a free pass on “pretentious.”) You’ll notice the word “evidence” is either placed in quotation marks in our literature or not used at all. That’s because PPI and other skeptical organizations are moving away altogether from the word "evidence," which for too long has been a catch-all classification in our field. Its sloppy use has been reinforced in paranormal television programming, where unsubstantiated, subjective claims are treated as though they're evidentiary support, and paranormal reality stars wax scientificky about reviewing their "evidence" like it's sure to be chock full of ghosty goodness (which, of course, it is—since it's TV). As amateur investigators and researchers, however, prejudging our data to be evidence encourages an expectation bias: believing that a source holds evidence, one tends to find it and present it as proof. As skeptical enquirers, PPI investigators prefer to believe that a source does not hold evidence, so when we've isolated an anomaly in our media for discussion and further analysis, it’s described merely as an event of interest.

“Interest,” however, can be used with hidden subtext. You already know that. For example, when someone tells you your poem is “interesting” and doesn’t say anything further, you know you’re fully in the weeds. Taken for its most literal meaning, “interest” is about the dividend you obtain from an investment, whether that’s a monetary investment, an inherently personal investment, or an investment of your attention. Not inconsequentially, when you aren’t inherently invested in an outcome, you’re “disinterested” in it, and when something is not worth “paying” attention to, you’re “uninterested” in it.

Whether in the pseudoscience of paranormal investigating or legitimate sciences, scientific method requires a system of checks and balances on disinterested objectivity and interested curiosity. From that standpoint, there are three kinds of “interesting”: noteworthy; intriguing; or compelling. These criteria help us to understand the classifications of EVP much better, as well as distinguish potential evidence from actual, credible evidence.


Types of Isolated Events

Events of interest falls into three main types:

Audible Voice Phenomenon (AVP)
Electronic Voice Phenomenon (EVP)
Context (CTX)

AVP: Sometimes referred to as "ghost voices," these phenomena are audible in the environment, to one's own ears, at the time they were captured.  In other words, they were noted in real time, so AVP are not electronic phenomena, but, rather, a record of one. It’s a misnomer that they are all audible “voice” phenomena, since they can range from the classic ghostly moan to the equally classic rapping on the cupboard door.  An AVP is initially acknowledged by its witnesses, without which we couldn’t know whether it’s an AVP or EVP. (Naturally, the reverse is also true: if a digital recorder is dropped in the woods and no one’s around to witness it, does it make a sound?) They’re disproved when surveillance logs or other audio sources indicate a practical cause.

EVP: Events not heard at the time of their occurrence, but instead "captured" on recorded audio, are EVP.  Just as "voice" is a misnomer, so too is "electronic," for the phenomenon has long existed in analog tape and phonographic recordings well before electronic audio devices became popular.

CTX: Events that are of interest for reasons other than their potential to be paranormal are flagged as context. In other words, they’re “un-phenomena.” There are a variety of reasons to do this. If someone in your audio announces a sudden and drastic drop in temperature, and you want to correlate that event to hourly meteorological data, it’s helpful to isolate that announcement for context. If a team member presents a finding determined to be an EVP, and you isolate the same event in your audio but it turns out to be a flushing toilet, it’s useful to isolate the flushing and present it as a context clip to explain your friend’s EVP. If clients or docents say something that’s of interest to the investigation, but it isn’t, itself, part of an anomalous event, it’s grist for context. And so on. You might have your own term for them (such as “reference”), but context clips are as vital to the peer review process as AVPs and EVPs because they help to build the case and get at the truth of things.


A Brief History of EVP Classification

team resources ernst senkowskiEVP research enjoyed its Golden Age during the 1970s, primarily in the study of instrumental transcommunication (ITC), a term coined by Physics professor and Hamburg native Ernst Senkowski (1922-2015). Senkowski is the first Honorary Nobel prize recipient for afterlife and paranormal scientific investigation. His 1979 book, Instrumentelle TransKommunikation, is considered by many to be the single most influential work in the field of ITC and electronic voice phenomena.

team resources friedrich jurgensonMany others, however, credit the origins of ITC research to Swedish dilettante, Friedrich Jürgenson (1903-1987), who first recognized disembodied voices in his analog recordings of birdsong. Jürgenson spent his life in the study of these phenomena, but his methodology and philosophy about them weren’t exactly objective. In 1971, he published his book, Voices from Space, in which he claimed he and his dog were receiving psychically transmitted extraterrestrial messages—which may sound bonkers to twenty-first century researchers of the phenomenon, but at the time was generally consistent with the underlying precepts of transcommunication.

team resources konstantins raudiveAt one time a student of Carl Jung, Latvian parapsychologist Konstantīns Raudive (1909 –1974)—frequently spelled "Konstantin" Raudive in the literature—was inspired by Jürgenson’s work and became a dedicated researcher of EVP. Experimenting with new methods of capture and categorizing their characteristics, Raudive is widely regarded as the first to apply a rigorous methodology to the research of EVP. He also took Jürgenson’s extra-terrestrial route for a while, perhaps out of loyalty to his eccentric progenitor, but eventually Raudive settled upon two likely causes for EVP:  thought-forms psychically imprinted onto the medium; or, voices of the dead rendered electromagnetically onto the medium. Raudive published the findings of his lifetime of research in his 1971 book, Breakthrough: An Amazing Experiment in Electronic Communication with the Dead.

team resources sarah estepAttracted to Raudive’s seeming empiricism and serious-minded methodology to the study of electronic voice phenomena, Sarah Wilson Estep (1928-2008) not only joined ranks with Konstantīns Raudive, she extended his research and brought it to the U.S.

In 1982 she launched, both, the American Association of Electronic Voice Phenomenon and her book, Voices of Eternity. In it, Estep lays out the three basic classifications according to clarity and volume:


Classification A EVP: "A clear and distinct voice or sound that is universally accepted and undisputed, because it must be understood by anyone with normal hearing and without being told or prompted to what is being said or heard. It can be heard without the use of headphones."

Classification B EVP: "A voice or sound that is distinct and fairly loud. This class of voice is more common and can be heard by most people after being told what to listen for. It is usually audible to experienced persons who have learned the skill of listening to EVP. It can sometimes be heard without the use of headphones."

Classification C EVP: "A faint and whispery voice or sound that can barely be heard and is sometimes indecipherable and unintelligible. It may have paranormal characteristics, such as a mechanical sound. Most investigators would apply objectivity and disregard it, but may save it for reference purposes."

As can be seen in her careful wording, Estep expresses concern about whether an EVP is trusted or disputed, whether it draws a consensus or should be objectively disregarded.  Why?  Because the reputation of the research is at stake, making EVP classifications a measure of risk as well as quality of data.

These are still useful standards by which to judge EVP.  However, the field has become increasingly skeptical of the research advanced by people like Estep and Raudive—and justifiably so. After all, building a case for EVP on the unsubstantiated existence of psychic transmissions poisons the milk from the get-go. And speaking of poisoning, radio frequency transmissions increased so much during the twentieth century that, not only are they sometimes hypothesized to be the source of some EVP, they may one day be our first wave of extraterrestrial contact.

I do feel strongly that those who dismiss all EVP researchers as unwitting victims of auditory pareidolia or stray RF gravely oversimplify the matter.  Not only can such detractors not claim to have performed longitudinal studies of the phenomenon as we have, they cannot know how rigorous our methodologies have been. Furthermore, without a doubt, there are definite, significant acoustic “signatures” that come with the most interesting anomalies, indicating something other than known causes.

However much these nattering naysayers might seem like buzzkills—especially the legitimate scientific and medical experts—they’re absolutely correct to make us work harder for our answers.  Extraordinary claims require extraordinary proof, and if we normalize bad or lazy science, we’ll never come close to obtaining credible evidence. More and more, serious, albeit amateur, researchers must factor these inconvenient explanations and hypotheses into their own determinations before even attempting an EVP classification, which only serves to make us better, more credible investigators.

It behooves us, then, to treat the phenomenon known as EVP as an objective event, and let the interpretation of it—or, eventually, the practical explanation of it—fall to a future generation that may one day understand the science of it better than we do. For that reason, once again, level of interest should remain a significant factor in our determinations, and we should avoid defaulting to the word “evidence.”  Hence,

a Class C EVP is a noteworthy event of interest;
a Class B EVP is an intriguing event of interest;
a Class A EVP is a compelling event of interest.



Many investigators like to put a little English on these basic categories and spin them into subclassifications. During an otherwise successful career that ended with their tragic deaths in September 2015, self-credentialed parapsychologists, EVP specialists, and celebrity couple Mark and Debbie Constantino also attempted to divide these EVP classifications into subcategories. True, they weren’t the first to do so, and their subclassifications are not universally recognized by the paranormal community.  However, they at least exemplify how even casual paranormal enthusiasts can experiment with subclassifications of their own:

  • Growling Voice EVP: self-explanatory;
  • Fast-Talking EVP:  said to operate at a higher frequency, and therefore communicate very quickly; one can pick out words, but only in piecemeal fashion;
  • Singsong EVP:  an EVP that comes through as if a spirit were singing it;
  • Whisper EVP:  the most common variety, this EVP is thought to be quieter because smaller amounts of energy are being used;
  • Altered EVP:  thought by some to be voice manipulation; very rare; will take a person's spoken words and transform or rearrange them into a spoken message;
  • Mimic EVP:  the "spirit" says one or more of the same words immediately after someone in the room has spoken them;
  • Multiple Spirit EVP:  one spirit begins the EVP, and one or more complete the thought or sentence (presumably in a different voice);
  • Layered EVP:  one EVP is spoken over another; or, an EVP is found underneath the voice of a real person speaking;
  • Reversed EVP: in a classification worthy of David Lynch’s Twin Peaks, verbal communication is recognized by reversing the audio clip; you might have already tried this one with a Beatles record.

In the interest of transparency, I should say that PPI does not use these subclassifications. In fact, our research strongly suggests that, with the exception of whisper and mimicry EVPs, most of these are likely to be matrixed artifacts of the digital recording process. Good cataloguing is a virtue, though, as long as it is done purposefully, consistently, and cautiously. In that regard, the Constantinos were inspiring because they got us thinking more categorically about what might possibly cause an anomalous audio capture to occur.

However, there’s a good lesson to be learned here as well: rather than assume all EVP are voices of the dead blathering at us through the ether, or that searching for them is like a Sudoku puzzle, we should instead treat all EVP as if they are perfectly explainable, and use the classification system to categorize our level of interest in them as anomalous events. 

A series of articles further discussing of each classification to isolate audio events of interest can be found elsewhere on this website.


  Use the link at the top of this page to open a PDF of this resource.